Field of the Invention and Description of the Prior Art
This invention relates to a method for administering drugs to warm blooded animals by oral or rectal delivery and it particularly relates to a method for enhancing the absorption of such orally or rectally delivered drugs from the gastrointestinal tract to the blood stream.
One known method of drug administration is accomplished by the incorporation of a drug in a "suppository", which generally speaking, is a medicated solid dosage form generally intended for use in the rectum, vagina, and to a lesser extent, in the urethra. Molded rectal suppositories usually employ vehicles that melt or soften at body temperatures so that the drug may be released for use. On the other hand, soft elastic gelatin capsule suppositories rely on the presence of moisture in the rectum which causes the capsule to open and release its contents which contains its therapeutic agent. Drugs administered in suppository form are administered for either local or systemic effect. The action of the drug is dependent on the nature of the drug, its concentration, and its rate of absorption. Although rectal suppositories are commonly used for the treatment of constipation and hemorrhoids, that is, for local effect, such rectal suppositories are also administered rectally for systemic action. A wide variety of drugs may be rectally administered, as by the use of suppositories, including, for example, analgesics, antispasmodics, sedatives, tranquilizers, and antibacterial agents.
Both oral and rectal drug administration has many advantages over other routes of drug administration, such as parenteral or topical administration. For example, many drug substances that are given parenterally have restricted use in that they are usually given in hospital or clinical settings.
Oral and rectal drug administration also have advantages over parenteral administration. For example, oral or rectal drug administration does not require highly trained personnel required for parenteral administration and also represents significantly less hazard to the patient, such as possible antigenicity development with certain drugs (e.g., hormones).
Also surface active agents have been used to increase gastrointestinal drug absorption, especially from the rectal compartment, although tissue damage is a significant concern. In view of the known disadvantages of parenteral drug administration, drug administration by oral or rectal route enables many drugs to be absorbed from the anorectal area and yet retain their therapeutic value. The lower hemorrhoidal vein, surrounding the colon and rectum, enters the inferior vena cava and thereby bypasses the liver. Therefore, drugs are absorbed directly into the general circulation when rectally administered.